People visit websites with all sorts of combinations of browsers, OS'es, and extensions -- and no matter how good of a test system you have, you'll never be able to accurately predict each combination and weird side effects will happen. All the more reason to avoid needless cruft that gets in the way of interoperability. Too many web designers seem to ignore this. It shouldn’t/needn’t be necessary to crunch through a raft of web analytics to learn that either. As my gran used to say, you don’t need to jump into the Clyde to find out if you’re going to get wet.
[ probably not really appropriate for this list, but ... ] we should have seen that this was inevitable when we first saw a URL in someone's advert on the side of a bus or lorry. our safe isolated nerd world grew an increasing intersection with the 'normal' world of late stage capitalism. so our organizations, such as ripe, ietf, ... felt the need to have their front facing presence be 'normal' marketing. i am no longer the primary customer, and i am still trying to get over it. i'm happy if it is even possible to find what i need on these sites with less than 42 clicks. so if the webfolk know how to make it easier and faster to get through those 42 clicks without invading my privacy, cool with me. of course, that last bit is, as you point out, not simple. randy